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GB/T 6728-2002 Q235B hollow rectangular steel tubes are manufactured from low carbon structural steel with good weldability, excellent forming properties, and high structural strength. They are commonly used in mechanical fabrication, construction, and general engineering due to their balanced mechanical performance and cost-effectiveness.
| Shape | Hollow rectangular section |
| Outer Dimension | 20×30 mm to 400×600 mm |
| Wall Thickness | 1.5mm ~ 20mm |
| Length | 4 m to 12 m (customized lengths available) |
| Surface Condition | Black, galvanized, or painted |
| Manufacturing Process | Hot rolled or cold formed, electric resistance welded (ERW) or seamless |
High Structural Strength – Suitable for load-bearing applications.
Good Weldability – Compatible with common welding processes.
Excellent Formability – Easy to cut, bend, and fabricate.
Corrosion Protection Options – Available with galvanized or painted surfaces.
Cost-Effective – Balanced performance-to-price ratio.
| Element | C (max) | Si (max) | Mn | P (max) | S (max) |
| Q235B | 0.20 | 0.35 | 0.35–0.80 | 0.045 | 0.045 |
| Property | Tensile Strength | Yield Strength | Elongation | Impact Energy | Modulus of Elasticity |
| Value | 375–500 | ≥ 235 | ≥ 26 | ≥ 27 | ~ 200 |
Q235B: Chinese standard low carbon steel with excellent forming, welding, and moderate strength. Equivalent to ASTM A36 in many applications.
Construction & Infrastructure: Building frames, bridges, guardrails, and scaffolding.
Mechanical Manufacturing: Machinery frames, equipment supports, and agricultural machinery.
Automotive Industry: Vehicle chassis, trailers, and transport containers.
Furniture & Decoration: Metal furniture frames, shelving, and displays.
General Engineering: Structural supports, frameworks, and fabrication projects.
ASTM A36 (USA) – Carbon structural steel with similar properties.
EN S235JR (Europe) – Non-alloy structural steel with comparable yield strength.
JIS SS400 (Japan) – General structural steel grade with equivalent performance.
IS 2062 E250 (India) – Structural steel with similar composition and applications.
A: manufacturer,also can do trading.
A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock, it is according to quantity.
A: Yes, we could offer the sample for free charge but need pay the cost of freight.
A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.
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Main Product:
Seamless Steel Tubes,
Welded Precision Steel Pipes ,
Automotive Steel Tubes,
Carbon steel tubes,
Stainless Steel Tubes,
Special Shaped Steel Tubes
